Electronic timing systems are commonly used for pool swimming races, with the recording of swimmers' start times, lap times (often referred to as split times), and finish times commonly being triggered by switches known as “touchpads”. Referring to FIGS. 1 and 1A, the touchpads are typically large, flat panels 16 mounted underwater against the end wall 14 of pool 10 at the end of each swimming lane 12, positioned for a swimmer to make switch-closing contact with his hands or feet at the end of each lap. The touchpads 16 receive switch-operating power from a timing system 30 located near the pool, and send timing signals through permanent “deck plate” outlets 20 connected by buried conduit 21 to the timing system 30.
An alternative to the permanent deck plate arrangement is a temporary deck cable (not shown, but well known) with touchpad and backup button connections similar to those in the deck plates. For illustration, the deck cable corresponds to buried conduit 21 in FIG. 1, but lies temporarily on the surface of the pool deck 18 and is removed when the race event is over. The touchpad, backup button, and any other auxiliary device connections on the deck cable correspond in placement and function to the connections in deck plates 20, but are spliced into the cable without the need for a rigid mounting structure, and are removed along with the cable at the end of the race event.
The timing system 30, illustrated schematically as a timing “box” or controller 32 located at the pool “office” 34 (often an elevated timing table with assorted printers, displays, power source, controls, the timing box and computer) associates a start time, split time, or final time with each hit, and records and displays the times, for example transmitting them to scoreboard 38 via conduit 31. To make sure that each swimmer's times are recorded in the event of a missed or faulty touchpad hit, it is common to have a human timer (FIG. 1A) on the pool deck 18 holding a manually-operated “backup button” switch 22, which is plugged into a corresponding touchpad's deck plate 20 to deliver a “hit” signal to the timing system similar to that provided by the touchpad.
The deck plates 20 often have auxiliary power/data connections for speakers, lights, horns, and other peripheral devices shown schematically at 36, allowing information to be communicated from the timing system back to the swimmers poolside.
The typical deck plate 20 is mounted flush in the concrete pool deck 18 adjacent each swimming lane 12. Touchpad 16 and backup button 22 are connected to deck plate 20 through cables 16a and 22a ending in plugs 16b and 22b plugged into deck plate outlets 20b. Plugs 16b and 22b and deck plate outlets 20b have mating metal electrical terminals 16c, 22c and 20c. Swim race timing systems are typically powered by low voltage DC electrical current, usually on the order of 5VDC, so any exposed or water-shorted metal plug connections are safe. But the pool deck 18 is usually awash in chlorinated water, which quickly corrodes the metal terminals 20c in the deck plates. Frequent cleanings of deck plate terminals 20c to prevent corrosion and maintain connection quality usually make the problem worse, by abrading or chemically damaging the metal terminal surfaces. Even temporary deck cable terminals can suffer corrosion, although with some effort corrosion can be minimized by removing the cables and drying their terminals between meets.
Another problem with prior poolside timing system connectors is the need to supply electrical current to the switch-closing contacts in the touchpads and backup buttons. Direct (DC) current tends to increase corrosion of the conductive surfaces, such that at least one prior patent has suggested using voltages as low as 0.25 VDC for the touchpads to reduce corrosion of the conductive metal touchpad surfaces. The lower the DC voltage, however, the greater the line losses through the relatively small gauge wire connecting the various timing system components using that voltage, and the more the system is susceptible to noise.